Project Summary/Abstract: Medical diagnostics and monitoring are critical components in modern medicine. Adequate medical devices are needed that are compact, light weight, easy to operate, reliable and therefore suitable to be operated outside of hospitals directly in doctors offices. Breath analysis is a noninvasive, patient friendly and a safe method to diagnose and monitor several diseases/malfunctions of patients. In CO2 diagnostic testing, a change of the 13 C/12C isotopic ratio is determined with respect to a basal baseline value. By applying different labeled compounds, patients can be screened for a variety of medical conditions including glucose utilization, pancreatic function, intestinal bacterial overgrowth, liver function, and H. pylori infections of the digestive tract. Although an established technique, breath tests will only be widely accepted and applied if cost effective devices are available. Vista Photonics proposes to develop a low-cost, compact, rugged, real-time, breath gas analyzer, suitable for determining the 13 CO2/12CO2 ratio at relevant levels to accurately measure dietary fat intake. The sensor technology developed on this project needs no sample preparation or purification and may additionally be applied to diagnose and monitor other diseases or detect other isotope ratios. The proposed instrument utilizes an absorption band in the 2.7 um wavelength range together with a short absorption path of only 10 cm. The balanced absorption coefficients and path length enable a very compact and simple instrument that is capable of meeting price points for which widespread distribution of breath tests may be effected. To reach the required measurement precision for the isotope ratio, proven high-performance wavelength modulation spectroscopy with single-frequency distributed feedback laser diodes is proposed which typically can determine absorbance down to 10-5. This Phase I project will provide proof-of-concept for an isotope ratiometer which will be easy to operate and can determine the carbon dioxide isotope ratio with a measurement precision of better than 1%. Project Narrative: A cost effective and easy to operate 13C breath analyzer is proposed that shall be capable of diagnosing fat maldigestion. In addition to this targeted application, the analyzer is generally suited for the 50 known 13C breath tests that address a variety of metabolism malfunctions and may initiate more widespread adoption of this non-invasive approach. [unreadable] [unreadable] [unreadable]